Checkup: Health news in brief

Published 4:54 pm, Friday, January 11, 2013

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Sugar-free gum and cavity prevention

Cleans and protects teeth. Helps prevent cavities. So say the most popular brands of sugar-free gum. But do their claims stand up to scrutiny?

Many brands contain an additive called xylitol, a natural sweetener known to fight cavity-causing bacteria. In practice, though, it's not clear that xylitol has much impact. Some research suggests that while sugar-free gum does prevent cavities, xylitol per se is not responsible. Instead, it is the act itself of chewing gum that seems to prevent cavities.

One new study, published this month in The Journal of the American Dental Association, seems to confirm this. The largest and most thorough look at the subject to date, the study tracked 691 adults recruited from dental clinics around the country for three years. The subjects were randomly assigned to groups consuming xylitol lozenges five times a day or a similar tasting placebo.

Ultimately, those who received the xylitol had no statistically significant reduction in cavities.

The analysis of international health data determined that American men had the lowest life expectancy among men in 17 countries, including wealthy European nations, Australia, Canada and Japan. U.S. women had the second-lowest life expectancy (only Danish women fared worse.)

A new study suggests that babies learn bits of their native languages even before they are born.

A baby develops the ability to hear by about 30 weeks' gestation, so he can make out his mother's voice for the last two months of pregnancy. Researchers tested 40 American and 40 Swedish newborns to see if they could distinguish between English and Swedish vowel sounds. The study is scheduled for future publication in the journal Acta Paediatrica.

The scientists gave the babies, ranging in age from 7 hours to 75 hours, pacifiers that counted the number of sucks they made. The researchers inferred the babies' interest in the sound by the amount of sucking.

American babies consistently sucked more often when hearing Swedish vowel sounds, suggesting that the infants had not heard them before, and Swedish babies sucked more when hearing English vowels.

Learning so quickly after birth was unlikely, the researchers concluded, so the babies' understanding the difference between native and nonnative sounds could be attributed only to prenatal learning.